A novel hybrid scheme for chaotic image encryption

Abstract

This paper presents a novel hybrid scheme for chaotic image encryption by means of both public-key cryptosystem and symmetric cryptosystem. In the public-key cryptosystem, the hash value of the plain image can be securely transmitted through a public channel by utilizing elliptic curve for generating public and private keys, embedding hash value, encrypting and decrypting embedded data, and finally restoring hash value in the receiver. Based on a 8-dimensional discrete-time hyper-chaotic system, a symmetric encryption method associated with the hash value of plaintext is then implemented, which achieves several mutually independent encryption operations, including position sequence and row-column cyclic shift for permutation, modulus and exclusive OR operations for diffusion. In particular, because of its passing NIST and TestU01 for random statistical properties, the proposed 8-dimensional discrete-time hyper-chaotic system can also be used to construct a higher-performance S-Box, acting as another crucial component in the chaotic image cryptosystem, so that its security can be further enhanced. Theoretical analysis and numerical experiments confirm the feasibility of the method.